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1.
FIKSEL (1988) provides an asymptotically unbiased kernel estimator for the density hs (r) of the spherical contact distribution function of stationary and isotropic point processes. This paper proposes alternative estimators of hs (r) for use with regular grid of locations. The existing estimator of hs (r) and the alternatives proposed in this paper are then tested out in a simulation study.  相似文献   

2.
To visualize a bird’s-eye view of an ensemble of proteomes for various species, we recently developed a novel method of mapping a proteome ensemble into Three-Dimensional (3D) vector space. In this study, the “proteome” is defined as the entire set of all proteins encoded in a genome sequence, and these proteins were dealt with at the level of the SCOP Fold. First, we represented the proteome of a species s by a 1053-dimensional vector x(s), where its length ∣x(s)∣ represents the overall amount of all the SCOP Folds in the proteome, and its unit vector x(s)/∣x(s)∣ represents the relative composition of the SCOP Folds in the proteome and the size of the dimension, 1053, is the number of all possible Folds in the proteome ensemble given. Second, we mapped the vector x(s) to the 3D vector y(s), based on the two simple principles: (1) ∣y(s)∣ = ∣x(s)∣, and (2) the angle between y(s) and y(t) maximally correlates with the angle between x(s) and x(t). We applied to the mapping of a proteome ensemble for 456 species, which were retrieved from the Genomes TO Protein structures and functions (GTOP) database. As a result, we succeeded in the mapping in that the properties of the 1053-dimensional vectors were quantitatively conserved in the 3D vectors. Particularly, the angles between vectors before and after the mapping highly correlated with each other (correlation coefficients were 0.95–0.96). This new mapping method will allow researchers to intuitively interpret the visual information presented in the maps in a highly effective manner.  相似文献   

3.
Cytological studies of African cultivated rice,Oryza glaberrima   总被引:1,自引:1,他引:0  
African cultivated rice, Oryza glaberrima Steud., was cytologically characterized by using both karyotype analysis and molecular cytology. The somatic chromosomes resemble those of Asian cultivated rice, Oryza sauva L., in general morphology, although some minor differences were noted. Multicolor fluorescence in situ hybridization (McFISH) with chromosomes detected one 45s (17s-5.8s-25s) ribosomal RNA gene locus (45s rDNA) and one 5s ribosomal RNA gene locus (5s rDNA) in the chromosome complement. The 45s rDNA and 5s rDNA loci were physically mapped to the distal end of the short arm of chromosome 9 and to the proximal region of the short arm of chromosome 11 respectively, as in O. sativa. Based on the cytological observations and the physical map of the rDNA loci, the chromosomal organization of O.glaberrima and O. sativa seems to be very similar.  相似文献   

4.
Studying the responses of soil respiration (Rs) to soil management changes is critical for enhancing our understanding of the global carbon cycle and has practical implications for grassland management. Therefore, the objectives of this study were (1) quantify daily and seasonal patterns of Rs, (2) evaluate the influence of abiotic factors on Rs, and (3) detect the effects of soil management changes on Rs. We hypothesized that (1) most of daily and seasonal variation in Rs could be explained by soil temperature (Ts) and soil water content (Sw), (2) soil management changes could significantly affect Rs, and (3) soil management changes affected Rs via the significant change in abiotic and biotic factors. In situ Rs values were monitored in an agropastoral ecotone in Inner Mongolia, China, during the growing seasons in 2009 (August to October) and 2010 (May to October). The soil management changes sequences included free grazing grassland (FG), cropland (CL), grazing enclosure grassland (GE), and abandoned cultivated grassland (AC). During the growing season in 2010, cumulative Rs for FG, CL, GE, and AC averaged 265.97, 344.74, 236.70, and 226.42 gC m?2 year?1, respectively. The Ts and Sw significantly influenced Rs and explained 66%–86% of the variability in daily Rs. Monthly mean temperature and precipitation explained 78%–96% of the variability in monthly Rs. The results clearly showed that Rs was increased by 29% with the conversion of FG to CL and decreased by 35% and 11% with the conversion of CL to AC and FG to GE. The factors impacting the change in Rs under different soil management changes sequences varied. Our results confirm the tested hypotheses. The increase in Q10 and litter biomass induced by conversion of FG to GE could lead to increased Rs if the climate warming. We suggest that after proper natural restoration period, grasslands should be utilized properly to decrease Rs.  相似文献   

5.
Summary A group of chlorophyll deficient mutants (br s mutants) of Chlamydomonas accumulates protoporphyrin and has poorly developed chloroplast membrane systems (Wang et al. 1974). In order to determine whether a poorly developed chloroplast membrane system is the reason for, or the result of, the inability of the br s mutants to metabolize protoporphyrin to chlorophyll, a second mutation was selected which restored chlorophyll synthesis in br s mutants. One such double mutant (br s-2 g-4) was analyzed. The double mutant br s-2 g-4 has partially restored chlorophyll synthesis, but has defective photosystem II and photosystem I electron transport as well as abnormal chloroplast ultrastructure. Since these defects are not present in cells carrying only the g-4 mutation, they are presumed to be caused by the br s-2 mutation. It is concluded that a defect in chloroplast membrane development resulting from the br s-2 mutation causes an apparent defect in magnesium chelation by protoprophyrin. This is consistant with evidence that chlorophyll biosynthesis from magnesium protoporphyrin to chlorophyll takes place on the chloroplast membranes.  相似文献   

6.
Abstract

Fifty-six strains of Pseudomonas syringae pv. tomato (P.s. pv. tomato) were collected from tomato-producing areas in Tanzania and assessed for resistance to copper and antibiotics. The collection was done from three tomato-producing regions (Morogoro, Arusha and Iringa), representing three different ecological conditions in the country. After isolation and identification, the P. s. pv. tomato strains were grown on King's medium B (KB) amended with 20% copper sulphate (w/v). The strains were also assessed for resistance to antibiotics. Results indicated that there was widespread resistance of the P. s. pv. tomato strains to copper sulphate. The highest level of resistance was recorded from the Arusha region (Northern Tanzania), 83.3% of the P. s. pv. tomato strains from that region showed resistance to copper sulphate. This was followed by Iringa region (Southern Tanzania), from where strains of the pathogen were moderately resistant to copper sulphate, such that 54.0% of them were able to grow on the KB medium amended with 20% (w/v) of the copper compound.

Out of seven strains of P. s. pv. tomato from Morogoro region (Central Tanzania) included in the study, five (71.5%) were resistant to copper sulphate. The only strain of P. s. pv. tomato from the Dodoma region (Central Tanzania, but with a different ecological condition from the Morogoro region) included in the study was unable to grow on the medium containing 20% copper sulphate. None of the P. s. pv. tomato strains in the four regions included in the study were resistant to streptomycin sulphate. These results suggest that in the Arusha and Iringa regions of Tanzania, there might be possibilities of excessive use of copper compounds in tomato production, such that strains of P. s. pv. tomato strains in the areas have become resistant to the compounds.  相似文献   

7.
Condensation of 2,3,4,5,6-penta-O-acetyl-l-bromo-1-s-methyl-l-thio- -glucito (1) with 6-chloro-9-(chloromercuri)purine gave 49% of crystalline, levorotatory (1s)-2,3,4,5,6-penta-O-acetyl-1-(6-chloropurin-9-yl)-1- -methyl-1-thio- -glucitol (3), together with a smaller proportion of the syrupy, dextrorotatory (1R) isomer. Thiourea converted 3 into its 6-mercaptopurine analog, whose O-deacetylated derivative could be s-methylated to the corresponding -(methylthio)purin-9-yl analog; all compounds in this sequence were crystalline and were the pure (1s) isomers, as were the corresponding 1′-s-ethyl derivatives prepared by a similar route. Crystal-structure analysis of the O-deacetylated derivative of the 1 s-ethyl analog of 3 established the relative stereochemistry of the ethylthio group, permitting assignment of the (1s) absolute stereochemistry to this compound and thus to all compounds in the sequence starting from 1, including the previously described, crystalline, levorotatory 1-(1,6-dihydro-6-thioxopurin-9-yl)-1-s-ethyl-1-thio- -glucitol, whose chirality at C-1 had not hitherto been established. The close similarity of the chiroptical properties of the crystalline 1′-s-methyl derivatives to those of their 1′-s-ethyl counterparts permitted firm attribution of (1s) chirality to the former series also. Conformational studies showed that all of the derivatives have the sugar chain in a non-extended (sickle) conformation.  相似文献   

8.
Spatially heterogeneous ecosystems form a majority of land types in the vast drylands of the globe. To evaluate climate‐change effects on CO2 fluxes in such ecosystems, it is critical to understand the relative responses of each ecosystem component (microsite). We investigated soil respiration (Rs) at four sites along an aridity gradient (90–780 mm mean annual precipitation, MAP) during almost 2 years. In addition, Rs was measured in rainfall manipulations plots at the two central sites where ~30% droughting and ~30% water supplementation treatments were used over 5 years. Annual Rs was higher by 23% under shrub canopies compared with herbaceous gaps between shrubs, but Rs at both microsites responded similarly to rainfall reduction. Decreasing precipitation and soil water content along the aridity gradient and across rainfall manipulations resulted in a progressive decline in Rs at both microsites, i.e. the drier the conditions, the larger was the effect of reduction in water availability on Rs. Annual Rs on the ecosystem scale decreased at a slope of 256/MAP g C m?2 yr?1 mm?1 (r2=0.97). The reduction in Rs amounted to 77% along the aridity gradient and to 16% across rainfall manipulations. Soil organic carbon (SOC) decreased with declining precipitation, and variation in SOC stocks explained 77% of the variation in annual Rs across sites, rainfall manipulations and microsites. This study shows that rainfall manipulations over several years are a useful tool for experimentally predicting climate‐change effects on CO2 fluxes for time scales (such as approximated by aridity gradients) that are beyond common research periods. Rainfall reduction decreases rates of Rs not only by lowering biological activity, but also by drastically reducing shrub cover. We postulate that future climate change in heterogeneous ecosystems, such as Mediterranean and deserts shrublands will have a major impact on Rs by feedbacks through changes in vegetation structure.  相似文献   

9.
Global warming intensifies the hydrological cycle, which results in changes in precipitation regime (frequency and amount), and will likely have significant impacts on soil respiration (Rs). Although the responses of Rs to changes in precipitation amount have been extensively studied, there is little consensus on how Rs will be affected by changes in precipitation frequency (PF) across the globe. Here, we synthesized the field observations from 296 published papers to quantify the effects of PF on Rs and its components using meta-analysis. Our results indicated that the effects of PF on Rs decreased with an increase in background mean annual precipitation. When the data were grouped by climate conditions, increased PF showed positive effects on Rs under the arid condition but not under the semi-humid or humid conditions, whereas decreased PF suppressed Rs across all the climate conditions. The positive effects of increased PF mainly resulted from the positive response of heterotrophic respiration under the arid condition while the negative effects of decreased PF were mainly attributed to the reductions in root biomass and respiration. Overall, our global synthesis provided for the first time a comprehensive analysis of the divergent effects of PF on Rs and its components across climate regions. This study also provided a framework for understanding and modeling responses of ecosystem carbon cycling to global precipitation change.  相似文献   

10.
 Molecular cytogenetics is a convenient tool to investigate the organization and evolution of plant genomes. In coniferous trees of the Pinaceae, cytogenetic data is rudimentary since individual chromosomes are difficult to distinguish and karyotypes of related species are poorly differentiated. We determined the chromosomal locations of ribosomal RNA genes in white spruce (Picea glauca) and Sitka spruce (Picea sitchensis) using fluorescence in situ hybridization. The biotin-labeled DNA probes consisted of the 5s ribosomal DNA (rDNA) amplified from white spruce using the polymerase chain reaction and a heterologous 18s-5.8s-26s rDNA sequence. The 5s rDNA was present only on chromosome 5 at a single locus and near to an 18s-5.8s-26s rDNA locus in both species. Additional 18s-5.8s-26s rDNA loci were found at interstitial sites on six and four chromosomes of white and Sitka spruce, respectively, providing potentially useful interspecific differences. Progress in karyotyping both species is presented. A molecular analysis of 5s rDNA of white spruce revealed the presence of two classes of repeating units, one of 221 bp corresponding to the PCR amplification product, and another of approximately 600 bp. The nucleotide sequence and copy number of the 221-bp class is reported. Received: 17 September 1996/Accepted: 20 December 1996  相似文献   

11.
Gas exchange was measured from 1 month before the onset of anthesis until the end of grain filling in field-grown spring wheat, Triticum aestivum L., cv. Vinjett, in southern Sweden. Two g s models were parameterised using these data: one Jarvis-type multiplicative g s model (J-model), and one combined stomatal-photosynthesis model (L-model). In addition, the multiplicative g s model parameterisation for wheat used within the European Monitoring and Evaluation Programme (EMEP-model) was tested and evaluated. The J-model performed well (R 2=0.77), with no systematic pattern of the residuals plotted against the driving variables. The L-model explained a larger proportion of the variation in g s data when observations of A n were used as input data (R 2=0.71) compared to when A n was modelled (R 2=0.53). In both cases there was a systematic model failure, with g s being over- and underestimated before and after anthesis, respectively. This pattern was caused by the non-parallel changes in g s and A n during plant phenological development, with A n both peaking and starting to decline earlier as compared to g s . The EMEP-model accounted for 41% of the variation in g s data, with g s being underestimated after anthesis. We conclude that, under the climatic conditions prevailing in southern Scandinavia, the performance of the combined stomatal-photosynthesis approach is hampered by the non-parallel changes in g s and A n, and that the phenology function of the EMEP-model, having a sharp local maximum at anthesis, should be replaced by a function with a broad non-limiting period after anthesis.  相似文献   

12.
Environmental and physiological regulation of transpiration were examined in several gap-colonizing shrub and tree species during two consecutive dry seasons in a moist, lowland tropical forest on Barro Colorado Island, Panama. Whole plant transpiration, stomatal and total vapor phase (stomatal + boundary layer) conductance, plant water potential and environmental variables were measured concurrently. This allowed control of transpiration (E) to be partitioned quantitatively between stomatal (g s) and boundary layer (g b) conductance and permitted the impact of invividual environmental and physiological variables on stomatal behavior and E to be assessed. Wind speed in treefall gap sites was often below the 0.25 m s–1 stalling speed of the anemometer used and was rarely above 0.5 m s–1, resulting in uniformly low g b (c. 200–300 mmol m–2 s–1) among all species studied regardless of leaf size. Stomatal conductance was typically equal to or somewhat greater than g b. This strongly decoupled E from control by stomata, so that in Miconia argentea a 10% change in g s when g s was near its mean value was predicted to yield only a 2.5% change in E. Porometric estimates of E, obtained as the product of g s and the leaf-bulk air vapor pressure difference (VPD) without taking g b into account, were up to 300% higher than actual E determined from sap flow measurements. Porometry was thus inadequate as a means of assessing the physiological consequences of stomatal behavior in different gap colonizing species. Stomatal responses to humidity strongly limited the increase in E with increasing evaporative demand. Stomata of all species studied appeared to respond to increasing evaporative demand in the same manner when the leaf surface was selected as the reference point for determination of external vapor pressure and when simultaneous variation of light and leaf-air VPD was taken into account. This result suggests that contrasting stomatal responses to similar leaf-bulk air VPD may be governed as much by the external boundary layer as by intrinsic physiological differences among species. Both E and g s initially increased sharply with increasing leaf area-specific total hydraulic conductance of the soil/root/leaf pathway (G t), becoming asymptotic at higher values of G t. For both E and g s a unique relationship appeared to describe the response of all species to variations in G t. The relatively weak correlation observed between g s and midday leaf water potential suggested that stomatal adjustment to variations in water availability coordinated E with water transport efficiency rather than bulk leaf water status.  相似文献   

13.
The 17s-5.8s-25s ribosomal RNA gene (rDNA) loci in Oryza spp. were identified by the fluorescence in-situ hybridization (FISH) method. The rDNA loci were located on one-to-three chromosomes (two-to-six sites) within the eight diploid Oryza spp. One of the rDNA loci gave the weakest hybridization signal. This locus is reported for the first time in the genus Oryza. The chromosomes containing the rDNA loci were determined to be numbers 9, 10 and 11 in descending order of the copy number of rDNA. The application of image analysis methods, after slide preparation treatments (post-treatments), and the use of a thermal cycler, greatly improved the reproducibility of the results. The evolutionary significance of the variability of rDNA loci among the Oryza spp. is discussed.  相似文献   

14.
T Matsumoto  A Teramoto 《Biopolymers》1974,13(7):1347-1356
The Zimm–Bragg parameters s and σ were determined for poly(γ-benzyl L -glutamate) (PBLG) in m-cresol and in dimethylformamide (DMF) from ORD data as a function of molecular weight. It was found that, within the temperature range between 10 and 55°C and on the average, s = 1.61 ± 0.1 and √σ = 0.04 ± 0.01 in m-cresol and s = 1.65 ± 0.05 and √σ = 0.045 ± 0.015 in DMF. The values of s in m-cresol decreased with increasing temperature, while the values of σ in the same solvent increased. This result for s suggests that PBLG in m-cresol will undergo a thermal helix–coil transition of normal type. The parameters in DMF showed no appreciable trend to vary with temperature. Aside from the difference between the two solvents, our results are consistent with existing data for various conformation-dependent properties such as light-scattering radius, intrinsic viscosity, and dipole moment, each indicating that the polypeptide chain has some flexibility in helicogenic solvents.  相似文献   

15.
A knowledge of genome organization is important for understanding how genomes function and evolve, and provide information likely to be useful in plant breeding programmes involving hybridization and genetic manipulation. Molecular techniques, including in situ hybridization, molecular cloning and DNA sequencing, are proving valuable tools to investigate the structure, organization, and diversity of chromosomes in agricultural crops. Heterologous labelled 18 s-5.8 s-25 s (pTa71) and 5 s rDNAs (pTa794) were used for in situ hybridization on Vigna unguiculata (L.) Walp. chromosomes. Hybridization with 18 s-5.8 s-25 s rRNA gene probes occurred at the same chromosomal sites which were positive to the CMA fluorochrome. Silver staining of nucleolar-organizing regions indicated that all the rDNA sites detected using the 18 s-5.8 s-25 s rRNA gene probe possessed active genes. Degenerate telomeric repeats gave hybridization signals at the telomeres of most chromosomes and no intercalary sites were detected at metaphase; the sequences appear to have no preferential distribution in interphase nuclei. A repetitive DraI family from V. unguiculata was cloned (pVuKB1) and characterized. The DraI repeat is 488 nucleotides long, AT rich (74%), and hybridized on all chromosomes in the centromeric areas. The presence of this sequence family was investigated by Southern hybridization in different Vigna species and other Leguminoseae. It was only detected in V. unguiculata, and hence represents a species-specific DNA sequence.  相似文献   

16.
Net photosynthetic rate (P N), transpiration rate (E), water use efficiency (WUE), stomatal conductance (g s), and stomatal limitation (Ls) were investigated in two Syringa species. The saturation irradiance (SI) was 400 µmol m-2s-1 for S. pinnatifolia and 1 700 µmol m-2s-1 for S. oblata. Compared with S. oblata, S. pinnatifolia had extremely low gs. Unlike S. oblata, the maximal photosynthetic rate (P max) in S. pinnatifoliaoccurred around 08:00 and then fell down, indicating this species was sensitive to higher temperature and high photosynthetic photon flux density. However, such phenomenon was interrupted by the leaf development rhythms before summer. A relatively lower P N together with a lower leaf area and shoot growth showed the capacity for carbon assimilation was poorer in S. pinnatifolia.This revised version was published online in March 2005 with corrections to the page numbers.  相似文献   

17.
Using a pair of congenic strains of mice differing only at the Mls haplotype (Mls locus and closely linked genes), BALB/c (Mls b ) and BALB.D2-Mls a , we have compared the in vitro proliferative responses of M1sb lymphocytes to M1sa antigens presented on either lymph node cells (LNC) or peritoneal adherent cells (PAC). Results showed that M1sa-PAC are stronger stimulators than M1sa-LNC, and furthermore, that the supernatant from M1sa-PAC may be effective in eliciting a lymphocyte proliferative response. The proliferation in response to PAC supernatant is partially due to activation by nonspecific factor(s); however, the response in the presence of M1sa incompatible PAC supernatant is about three times greater than the response obtained in the presence of syngeneic M1sb-PAC supernatant, suggesting an additional stimulation by soluble M1sa antigens. Contrasting with the ability of PAC-supernatant to stimulate a primary proliferative response in vitro, the in vivo immunization of Mlsb mice with M1sa-PAC supernatant abrogates the specific proliferative response in subsequent one-way mixed lymphocyte cultures. This abrogation of the specific response is comparable to that observed after immunization with intact M1sa peritoneal or spleen cells, although in the latter case the anti-H-2 proliferative response is also decreased, regardless of whether the H-2 incompatible stimulating cells express an additional incompatibility for M1sa. The proliferation of untreated, but not of M1sa-immunized BALB/c LNC, is stronger in cultures with DBA/2 stimulating cells (incompatible for M1sa and other non-H-2 antigens) than in cultures with BALBM-Mls a cells (incompatible for M1sa alone), and is comparable in intensity to that activated by H-2 incompatibility. We conclude that M1sa antigens are more efficiently recognized by unprimed helper T cells when presented on PAC than when presented on LNC. In the primary proliferative response, the effects of M1sa and other non-H-2 antigens may be cumulative. In vivo immunization against M1sa antigens results in suppression of the specific proliferative response and, to a certain extent, of the nonspecific proliferative response (directed against both H-2 and other non-H-2 antigens). Since M1sa antigens are obtainable in soluble form, their physicochemical purification can now be envisaged.  相似文献   

18.
We evaluate for the first time the effect of Wolbachia infection, involving two different supergroups, on the structure and dynamics of the hybrid zone between two subspecies of Chorthippus parallelus (Orthoptera) in the Pyrenees. Wolbachia infection showed no effects on female fecundity or a slight increment in females infected by F supergroup, although in the last case it has to be well established. Cytoplasmic incompatibility (CI) is confirmed in crosses carried out in the field between individuals from a natural hybrid population. This CI, registered as the relative reduction in embryo production (sh), was of sh = 0.355 and sh = 0.286 in unidirectional crosses involving B and F supergroups, respectively. CI also occurred in bidirectional crosses (sh = 0.147) but with a weaker intensity. The transmission rates of the two Wolbachia strains (B and F) were estimated by the optimization of a theoretical model to reach the infection frequencies observed in certain population. To fit this scenario, both supergroups should present transmission rates close to 1. Further, we have simulated the infection dynamics, and hence, the capacity of Wolbachia to structure the population of the host insects and to affect to reproduction and genetic introgression in the hybrid zone. This represents a first example of the influence of Wolbachia in an insect natural hybrid zone.  相似文献   

19.
Abstract Two new species of water mites, Pionopsis (s.s.)longicosta sp. nov. and Pionopsis (s.s.) zhaoi sp. nov. are described in the present paper. This is the first record of the genus of the subfamily Tiphyinae in the family Pionidae from China.  相似文献   

20.
SARAH (Software for theAssessment of antibioticResistance toAleyrodidae inHost plants) is a deterministic simulation model of whitefly population growth based on whitefly life-history components determined on individual plants. The life-history components recorded were oviposition rate, adult survival, pre-adult survival, developmental period, and sex ratio. The simulation model serves as a tool to combine these components and to obtain a single criterion for (antibiotic) resistance. The criterion used was the decrease in simulated intrinsic population growth rate, r s , relative the r s value determined on a susceptible control genotype. This model-based evaluation method was tested using the greenhouse whitefly,Trialeurodes vaporariorum Westwood, on tomato and the sweetpotato whitefly,Bemisia tabaci Gennadius, on tomato, eggplant, collard, and pepper. To study its consistency over time, the evaluation method was repeated six times forT. vaporariorum on a susceptible and a resistant tomato cultivar. Simulated intrinsic population growth rate was more consistent in indicating resistance than any of the individual life-history components. Of tenL. hirsutum accessions tested for resistance toT. vaporariorum, three exhibited r s values that were significantly lower than those for the susceptible control. In addition, on these tenL. hirsutum accessions, a significant positive correlation was observed between r s and sex ratio (# females/# males). Four host plant species (tomato, collard, eggplant, and pepper) were evaluated for resistance toB. tabaci. All life-history components and r s values varied among host species, while a negative r s value was observed forB. tabaci on pepper. A high correlation was found between results from a sensitivity analysis of SARAH and results from a sensitivity analysis of a validated whitefly population simulation model by Yanoet al. (1989a). Significant correlations were found for the relationships between oviposition rate, adult survival, or pre-adult survival and r s , indicating that none of these life-history components can be omitted from the test procedure. This model-based evaluation method offers a standardized way to quantify levels of antibiotic resistance to whiteflies and will enhance efficiency in breeding programs.  相似文献   

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